Analysis of low viscosity liquid and/or powder samples to determine the presence of analytes, (eg. trace elements and/or contaminates etc.), present therein, is often accomplished by "nebulization", followed by injection of said nebulization products into a detector system which can be comprised of, for instance, an Inductively Coupled Plasma-Atomic Emission Spectrometer (ICP-AES) or an Inductively Coupled Plasma-Mass Spectrometer (ICP-MS) system. Nebulization of low viscosity liquid sample or solvated powder sample, for instance, can often be easily achieved by Pneumatic, Direct Injection and Ultrasonic etc. sample nebulizer systems. Said nebulizer systems generally produce numerous small diameter droplets of analyte containing liquid, (eg. solvent), which, typically after desolvation, are suitable for injection into an Inductively Couple Plasma (ICP). (Note that a patent to Zhu et al., U.S. Pat. No. 5,259,254 describes an Ultrasonic Nebulizer system and a patent to Wiederin, U.S. Pat. No. 5,212,365 describes a Direct Injection Micronebulizer System).
High viscosity liquid samples, however, often can not be directly subjected to nebulization because of their viscosity limited flow properties. As a result, known sample preparation methods such as Ashing, Acid Digestion and/or Organic Solvent Dilution are practiced to provide a sample which can be effectively nebulized by typical nebulizer systems, and entered to an ICP-AES and/or ICP-MS. It is well recognized, however, that said Ashing, Acid Digestion and/or Organic Solvent Dilution sample preparation approaches are tedious and time consuming and practice thereof often does not result in desired sample analysis sensitivity and accuracy. The ashing approach, for instance, (which utilizes an oven or microwave source to convert a sample to an ash), often results in vaporization of, poor recovery of, and poor detection of highly volatile elements, (eg. boron, vanadium, arsenic, sulfur and phospherous), and as mentioned, said procedure can be very time consuming. The acid digestion approach, (which involves digestion of a sample by an acid (eg. nitric), followed by mixture with a solvent), is also very tedious and time consuming. For emphasis, it is noted that a simple low viscosity liquid sample nebulization procedure might require one (1) minute or so to practice, while an acid digestion might require, relatively speaking, four (4) to eight (8) hours. As well, the Organic Solvent Dilution approach often leads to introduction of added volatile organic solvents into a subsequently utilized ICP, and said volatile organic solvents can cause plasma instability and low analyte detection sensitivity.
An alternative sample preparation approach, which can produce effectively "nebulized" sample products appropriate for entry to an ICP, involves Laser Ablation. (It is noted that the practice of Laser Ablation involves application of focused Laser contain energy onto a sample, and requires on the order of seconds to practice). It is known that Laser Ablation is very well suited to use with solid samples, however, when Laser contained energy is applied to liquids and/or powder samples, the result often includes "splattering", "splashing" and/or "scattering" effects, rather than, (or in addition to), the desired effective "nebulization" effects. To date said "splattering", "splashing" and/or "scattering" effects have made application of Laser Ablation to "nebulize" liquid and/or powder samples impractical. A system and method which would essentially eliminate said "splattering", "splashing" and/or "scattering" effects, and which would allow Laser contained energy to be applied to a liquid and/or powder sample with the primary result being production of effectively "nebulized" sample, would therefore be of great utility. The present invention provides such a system and method.
With the foregoing in mind a search of patents was conducted with the result being that very little was found. A patent to Carlhoff et al., U.S. Pat. No. 5,537,207, however, was identified, as was a patent to Kirkpatric et al., U.S. Pat. No. 5,194,910. The former patent describes use of Lasers to produce a plasma from which are emitted wavelengths that identify the carbon-black content in materials, while the later patent describes spectroscopic analysis of light transmitted through oil. No known prior art, however, describes or even remotely suggests the sequestering of liquid and/or powder samples in pores present in a microporous membrane prior to application of Laser contained energy thereto to ablate said combination liquid and/or powder sample and microporous membrane, with the result primarily being effective "nebulization" of said liquid and/or powder sample, without accompanying, undesirable "splattering", "splashing" and/or "scattering". The present invention teaches such a utility providing system and method.